The invention relates to air pollution control apparatus such as dust collectors, and more particularly to such apparatus as utilize a reverse stream of compressed air to periodically clean the filter medium in dust collectors.
It is known to utilize a reverse pulse of compressed air to clean contaminants which have accumulated on the filter medium of a dust collector. The filter medium acts essentially as a seive, retaining the dust on one side and preventing it from passing through to the other side. As a layer of dust builds on the surface of the filter medium, increased amounts of energy are required to force air through the filter medium. Accordingly, it is desirable to periodically remove the build-up or cake of contaminants which collects on the filter medium.
Various arrangements have been proposed for directing a reverse pulse of air into a dust collector filter assembly to clean the filter medium. A potential problem with the use of such air pulses is that they may remove the contaminants or cake from only a portion of the filter medium, leaving the remainder of the filter medium uncleaned. This can happen when the air pulses impinge directly upon a portion of the filter medium and blow the contaminants off that portion of the filter medium. This prevents the pressure in the filter assembly from building to a sufficient level so as to blow the contaminants off the remainder of the filter medium.
It is known to use a sleeve located in the inlet end of a filter assembly for preventing air pulses from impinging upon the filter medium of the filter assembly. This is described in Klimczak U.S. Pat. No. 4,578,092, issued Mar. 25, 1986 (application Ser. No. 548,911, filed Nov. 4, 1983).